The production of phosgene by the reaction of chlorine with carbon monoxide in the presence of a carbon catalyst is a well known process. The phosgene produced by this process will typically contain 400 to 500 ppm by weight carbon tetrachloride. This amount, needs to be evaluated on the basis of the total world-wide production of phosgene which is about ten billion pounds (4.5.times.10.sup.9 kg), corresponds to co-production of about 4 to 5 million pounds (1.8.times.10.sup.6 kg to 2.3.times.10.sup.6 kg) of carbon tetrachloride with the phosgene.
A Japanese patent publication (Kokoku) Patent No. Hei 6[1994]-29129 discloses that the amount of carbon tetrachloride produced during the phosgene manufacturing process can be reduced by about 50% to about 150 ppm by weight by using an activated carbon which has been washed with an acid and which contains a total of 1.5 wt. % or less of metal components comprised of transition metals, boron, aluminum and silicon.
Carbon tetrachloride has been shown to have both significant ozone depletion and global warming potentials. Therefore, there is an interest in developing phosgene processes in which the amount of carbon tetrachloride impurity is minimized.
Silicon carbide has long been known as a material which has high thermal and chemical stability, has excellent heat and electrical conducting properties and as an abrasive which is almost as hard as diamond. Silicon carbide can be commercially prepared electrochemically using the Acheson process. The product so produced has a surface area of less than 1 m.sup.2 /g; its use as a catalyst support has been limited partly because of this low surface area. Recently, high surface area (60 to 400 m.sup.2 /g) silicon carbides have been prepared (M. J. Ledoux et al., J. Catal., 114, 176-185 (1988)). These high surface area materials are used as catalyst supports or carriers.